Question

Practical 1. D is a solution containing ethanedioic acid. E is a solution of sodium hydroxide. (a) Put D into the burette and titrate against portions of E using phenolphthalein as indicator. Repeat to obtain concordant titre values. Tabulate the results and calculate the average volume of acid used. (b) From your results and the information provided, calculate the: (i) concentration of D; (ii) value of x in D=(COOH)2·xH2O; (iii) volume of solution D that would neutralize a solution containing sodium hydroxide.

Accepted Answer

This is a titration practical. (a) Average titre = (sum of concordant burette readings)/number of readings, e.g. an average volume of acid used ≈ 24.6 cm³ (sample data). (b) Using the balanced equation H2C2O4 + 2NaOH → Na2C2O4 + 2H2O and the relation CaVa/CbVb = na/nb, the concentration of D is calculated from the known concentration and volume of E used, e.g. Ca = (Cb×Vb×na)/(Vb×nb). (ii) The value of x is found by comparing the calculated molar mass of the hydrated acid to the theoretical formula mass of (COOH)2·xH2O. (iii) The volume of D needed to neutralize a given amount of NaOH is found using the mole ratio from the balanced equation.

WAEC Chemistry 2021 Theory — Question 30

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